Inhalant anesthetic compositions and method

ABSTRACT

THE NOVEL COMPOUNDS 2,2-DIFLUOROETHYL DIFLUOROMETHYL ETHER AND ITS 1-CHLORO DERIVATIVE HAVING THE FORMULA CHF2CHCI-O-CHF2 ARE DISCLOSED. THE LATTER COMPOUND CAN BE PREPARED THROUGH CHLORINATION OF 2,2-DIFLUOROETHYL DIFLUOROMETHYL ETHER WHICH IN TURN CAN BE MADE BY REACTION OF 2,2-DIFLUOROETHANOL AND DIFLUOROCHLOROMETHANE IN THE PRESENCE OF AQUEOUS SODIUM HYDROXIDE. THE NOVEL COMPOUNDS ARE USEFUL AS INHALATION ANESTHETICS AND AS SOLVENTS AND DISPERSANTS FOR FLORINATED MATERIALS.

I INHALANT'ANESTHETIC COMPOSITIONS X ,AND METHOD 7 Ross C. Terrell, Plaiufield, N..l.,- assiguor to Airco, Inc., New York, N.Y. No Drawing. Filed July 2, 1971, Ser. No. 159,512

Int. Cl. A61k 27/00 6 Claims ABSTRACT. OF THE DISCLOSURE Thejn'ovel compounds 2,2-difluoroethyl difluoromethyl ether"'an'd its l-chloroderivative having the formula CHFCHClO--CHF are disclosed. The latter compound can be prepared through Chlorination of 2,2-difiuoroethyl di fluoromethyl ether which in turn can be made by reaction of 2,2-difluoroethanol and difluorochloromethane in the presence of aqueous sodium hydroxide. The novel compoundsare useful as inhalation anesthetics andas solvents and dispersants for fluorinated materials.

This invention relates-to the compounds 2,2-difluoro- -'et-hyl. difluoromethylether and l-chloro-2,2-difluoroethyl I'difiuoromethylether; and their use in producing anes- '.thesia in -anesthetic-susceptible, air-breathing mammals.

The compounds have the formula CHF CHY-O-CHF 'wherein Y is hydrogen or chlorine.

The compound 2,2-difluo-roethyl difluoromethyl ether has the following formula:

. This ether is normally a clear, colorless liquid with an ;.ethereal odor, andhas the following physical properties: boiling .point 55 C.; vapor pressure 225 mm. at 25 C.;

specific gravity 1.34; refractive index N 1.2966 and molecular weight 132.

The compound 1 chloro 2,2 difiuoroethyl difluoromethyl ether has the following formula:

ether is normally a clear, colorless liquid with an mammalsi'These' ethers are also easily miscible with other organic liquids including fats and oils and have useful solvent properties, for example,.as a solvent for fluorinated olefins and other fluorinated materials such as tluoro waxes. The compounds may-be-used to prepare pastes and dispersions of such materials useful for coatings and the like, and may be used as degreasing agents.

The compound 2,2-difluoroethyl difluoromethyl ether can be made by reacting 2,2-difluoroethanol with difluorochlo-romethane in the presence of aqueous sodium hydroxide which neutralizes the hydrogen chloride formed by the reaction. At the completion of the reaction the desired ether product can be separated from the reaction mixture by fractional distillation.

The compound 1 chloro 2,2 difiuoroethyl difluoromethyl ether can be prepared by chlorinating 2,2-difluoroethyl difiuoromethyl ether. The chlorination can be carried out in either a fully or partially transparent vessel so that photo energy can be supplied to the reaction. Suitable sources of photo energy are incandescent, ultraviolet and fiuoroescent lamps and even strong sun light. In view of the ready availability, low cost and ease of handling of incandescent lamps, they are preferred for use as the illumination source.

UnitedStates Patent "ice The chlorination reaction can be carried out by bubwhile it is strongly illuminated. The chlorine is added at the same rate at which it reacts which can be determined by checking for chlorine vapor in the eifiuent from the chlorinator. The reaction is exothermic so cooling water should be supplied to the chlorination apparatus to control the reaction. The chlorination can be carried out at any temperature from C. up to the boiling point of the chlorination mixture. Best results are usually found at -35 C. where the reaction rate is fast enough and the formation of by-products does not present a serious problem.

The eflluent from the chlorination apparatus can be passed through a water scrubber to dissolve the HCl which is formed. The chlorination should be continued until 0.8 to 1 mole of HCl per mole of starting ether is detected by titration of the dissolved HCl with a standard base. The extent of the chlorination can be controlled by the amount of chlorine bubbled through the ether and determined by the amount of effluent HCl. If too little HCl is evolved it indicates that the chlorination is slow. If too much HCl is determined it indicates that polychloro products have been formed or that the ether has decomposed into undesirable chlorinated reaction products.

Following the chlorination the reaction mass can be a separated by fractional distillation or by vapor phase chromatography. If distillation is employed it is recommended that the pressure be reduced in view of the high molecular weight of the product CHF CHClO CHF Excessive heating should be avoided in view of the possibility of decomposition of the desired product.

The following examples will illustrate the preparation of the novel ethers of this invention.

EXAMPLE I Synthesis of CHF CH OCHF 50% aqueous sodium hydroxide solution (284 g.) was added slowly to a mixture of CHF CH 'OH (82 g.) and CHF CI (Freon 22) (86 g.) in a 500 cc. stirred autoclave while holding the temperature at 25-60 and the pressure at 50-150 p.s.i. At the end of the reaction, the product 2,2-difluoroethyl difluoromethyl ether was isolated .by fractional distillation to give 60 g., B.P. 55, N 1.2966. The product was flammable and analyzed as follows:

Calc. for C H F O (percent): C, 27.3; H, 3.0. Found (percent): C, 27.2; H, 2.6.

EXAMPLE 11 Synthesis of CHFgCHClOCHF 43.2 grams of CHF CH OCHF were added to a water-jacketed chlorinator fitted with a thermometer, a Dry-Ice cold finger type condenser and a fritted glass gas dispersion tube. The reaction was carried out at 25 C. with gaseous chlorine being bubbled through the solution which was exposed to a source of illumination. The efiluent HCl was collected in a scrubber and aliquots were titrated with a standard base. The reaction was continued until one mole of H01 per mole of ether was titrated. The product CHF CHClOCHF was recovered by distillation and preparative gas chromatography, B.P. 74 C., N 1.3351. This product had borderline flammability.

Calculated formulation of C H CIF O (percent): C, 21.61; H, 1.81; F, 45.56. Found (percent): C, 21.73; H, 1.87; F, 45.45. x

The structure CHF CHCl--OCHF was confirmed by determination of the nuclear magnetic resonance spectrum.

In order to determine the potency of 2,2-difluoroethyl difiuoromethyl ether and 1-chloro-2,2-difiuoroethyl difiuoromethyl ether as inhalation anesthetics in respirable mixtures containing life-supporting amounts of oxygen, several tests were carried out employing mice. The compounds tested were at least 99.5% pure as determined by vapor phase chromatography.

The compound 2,2-difluoroethy difiuoromethyl ether, for example, was administered to test mice by a standard procedure in which a measured quantity of the agent is placed in a laboratory jar and allowed to completely evaporate so as to give a calculated vapor concentration. The test mice are then quickly placed in the jar and observed. Anesthesia is determined by observing the righting reflex of the mice. In such tests the 2,2-difiuoroethyl difiuoromethyl ether induced anesthesia of the mice in approximately 10 minutes at 5% vapor concentration. Some slight irritation in the test animals was possibly noticed. Recovery was observed to take place in one minute, illustrating the value of the test compound as a mild anesthetic, useful, for example, where a relatively greater amount of control over the patient is desired. Recovery time is measured beginning when the test mice are transferred from the test jar to room air and ending when the mice are observed to be able to walk. There were no delayed deaths.

A similar test was conducted with 1-ch1oro-2,2-difluoroethyl difiuoromethyl ether. With 1% concentration of this agent, induction occurred at 1 minute and 17 seconds and recovery at 1 minute and 33 seconds. At 1.5% concentration, induction took 41 seconds and recovery took 4 minutes and 48 seconds. At 2.5% concentration, induction time was down to only 12 seconds, while recovery required more than minutes. The agent produced some irregular muscle movements at the highest concentration and occasional movements throughout the test period when using the lowest concentration. There were no delayed deaths.

The compound 1-chloro-2,2-difluoroethyl difiuoromethyl ether is a potent anesthesia agent which is rapidly taken up and excreted by warm-blooded mammals. The compound also has analgesic properties. The recovered animals appeared fully alert. In comparison with the l-chloro-2,2,2-trifiuoroethyl difiuoromethyl ether anesthetic agent of my US. Pat. No. 3,535,425, 1-chloro-2,2- difluoroethyl difiuoromethyl ether gives less induction times at comparable concentrations. Thus with mice, 2.5 of the agent of my prior patent gave an induction time of 30 seconds while 2.5 of this anesthesia of this invention showed an induction time of only 12 seconds.

The anesthetic agents of the invention may be administered by any of the well known techniques used for the administration of general inhalation agents, such as the open drop, semiclosed, and closed systems. The agents may also be administered as an injectable anesthetic as taught by John C. Krantz, Jr., in US. Pat. 3,216,897, issued Nov. 9, 1965, and assigned to the assignee of the instant application.

The compounds of this invention lend themselves to eifective use as inhalant anesthetics in respirable mixtures containing life-supporting concentrations of oxygen as well as mixtures containing oxygen and other inhalation anesthetics such as nitrous oxide. The effective amount of the ethers of this invention to be employed depends on the level of anesthesia to which the mammal is to be brought, the rate at which anesthesia is to be induced, and the length of time over which anesthesia is to be maintained. Minor volume percentages of the ethers in oxygen from a fraction of a percent of the ethers, for instance, at least about 0.5%, up to several percent, e.g. up to about 8%, can be employed. The amount of anesthesia to be used can be easily regulated, starting with a small amount of the ether and gradually increasing the amount until the desired plane of anesthesia is reached. By then monitoring the physical reactions of the mammal, as is the usual procedure, the duration and plane of anesthesia can be readily controlled.

While there has been described what are at present considered to be the preferred embodiments of the invention, it will be understood that various modifications may be made therein which are withinthe true spirit and scope of the invention.

I claim:

1. An inhalant anesthetic composition comprising a member selected from the group consisting of 2,2-difluoroethyl difiuoromethyl ether and 1-chloro-2,2-difluoroethyl difiuoromethyl ether in admixture with oxygen in suitable proportion for anesthesia.

2. The composition of claim 1 in which the selected member is 2,2-difluoroethyl difiuoromethyl ether.

3. The composition of claim 1 in which the selected member is 1-chloro-2,2-difiuoroethyldifiuoromethyl ether.

4. A method of anesthetizing an inhalation anestheticsusceptible mammal which comprises administering to said mammal by inhalation an efiective, anesthetic amount of a member selected from the group consisting of 2,2-difluoroethyl difiuoromethyl ether and 1-chloro-2,2-difiuoroethyl difiuoromethyl ether along with suflicient oxygen to support life.

5. The method of claim 4 in which the selected member is 2,2-difiuoroethyl difiuoromethyl ether.

6. The method of claim 4 in which the selected member is 1-chloro-2,2-difluoroethyl difiuoromethyl ether.

References Cited UNITED STATES PATENTS 3,535,425 10/1970 Terrell 424-342 OTHER REFERENCES Larsen: Fluorine Chemistry Reviews, vol. 3, 19 69, p. 38. Y

JEROME D. GOLDBERG, Primary Examiner US. Cl. X.R. 260614 F 

